To minimize activated sludge generated during biotreatment, OPTC collaborates with Academia Sinica on an experiment to pulverize the cell walls of the sludge cells with ultrasound. The pulverized cells are fed to the bacteria in the anaerobic tank. This approach is effective in reducing sludge and generating biogas. A 4-month experiment was conducted in 2020 at the pilot plant. The results indicate that the system reduced sludge by 58% and increased biogas by 19%. The exceptional results prompted the plant to install the sludge reduction system in 2021.